Problem: Simplify the following expression: $r = \dfrac{10}{2t - 10} \div \dfrac{4}{8t}$
Explanation: Dividing by an expression is the same as multiplying by its inverse. $r = \dfrac{10}{2t - 10} \times \dfrac{8t}{4}$ When multiplying fractions, we multiply the numerators and the denominators. $r = \dfrac{ 10 \times 8t } { (2t - 10) \times 4}$ $r = \dfrac{80t}{8t - 40}$ Simplify: $r = \dfrac{10t}{t - 5}$